1) The yaw damper is disengaged, hydraulics are turned OFF, and GO is pressed. The stimulus at input 4 is removed and a 10v dc stimulus is applied to input 5 at the airspeed gain circuit and airspeed gain is read at 7. Test time is approximately 1 second.
(i) Test 8 - Rate Gyro 1) The yaw damper is disengaged, hydraulics are off and GO is pressed. The stimulus at input 3 is removed and the rate gyro is torqued. The rate gyro demodulator output is read at 2. Test time is approximately 1 second. Torquing stimulus is removed from the rate gyro at the end of the test.
2) The BITE switch is returned to OFF at the end of the tests. Hydraulics are applied and the yaw damper coupler is engaged for normal operation. YAW DAMPER SYSTEM - TROUBLE SHOOTING
5C1
22-12-0 Page 14 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. Jun 20/85
EFFECTIVITY
SA SZ-SIA and on SD ST-AIB and on WA N235WA thru N241WA GJ B-2509 and B-2510
Except aircraft with coupler P/N 4084042
1. General
NOTE: For aircraft with coupler P/N 4084042 installed (incorporating SB 27A1206), see 22-12-01.
A. The following trouble shooting procedures are intended to help trouble shoot the yaw damper system down to a component level. Trouble shooting charts are based on possible failure reports which may occur and the corresponding isolation procedure to detect and replace the faulty component. The charts are listed under the system heading and are separated into engage problems or operational problems.
B. Yaw Damper System
(1)
Trouble shooting the yaw damper system operational faults can be accomplished fairly quickly through use of the system test circuits. The yaw damper test switch on the center instrument panel torques the rate gyro in the yaw damper coupler. With hydraulic and electrical power on and the system engaged, a complete check of the system is made as indicated on the yaw damper indicator on the center instrument panel and observed rudder movement. If the system is faulty, the yaw damper coupler is usually at fault.
(2)
Yaw damper coupler has BITE controls on the front panel. Operation of BITE controls checks the majority of the signal paths in the system (Ref Yaw Damper System -Adjustment/Test). Proper analysis of the BITE indications, while performing a test of the coupler, helps indicate whether the coupler is at fault or a fault is at the rudder hydraulic power pack (Ref Yaw Damper System Trouble Shooting Chart and BITE Test Failed Chart). It should be noted that the autopilot warning light illuminate if a BITE switch on the yaw damper coupler is positioned to ARM.
(3)
Trouble shooting yaw damper system engage faults involves checking the operation of the autopilot accessory box, and yaw damper coupler. If the yaw damper system does not engage or has nuisance trips, the fault will probably be in one of the accessory boxes (Ref Yaw Damper System Engage Trouble Shooting Charts).
(4)
The solenoid valves, transfer valves and position transducers on the hydraulic power pack have proven to be very reliable. Operational problems will more than likely be traced to relays in one of the autopilot accessory boxes. Hydraulic power pack problems are usually indicated by operational faults when the yaw damper system is not engaged, such as sloppy centering of the rudder due to hydraulic wear or leaking seals (Ref Chapter 27, Flight Controls).
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
(5) Before trouble shooting the yaw damper system, ensure hydraulic and electrical power is applied to the airplane and the rudder operates normally without the yaw damper system engaged. The flight control system B switch must be on to engage the yaw damper system. Ensure the yaw damper system, master caution, master dimming bus indicator lights, dim and test, autopilot engage interlock and warning light circuit breakers are closed before attempting to engage the yaw damper system. To prevent misleading indications, test operation of the autopilot disengage lights by pressing lenses to ensure bulbs illuminate. It should be noted that the yaw damper engage light is normally illuminated whenever the yaw damper system is not engaged. The central air data computer does not have to be energized for self-test of the yaw damper system since no interlock voltages are provided to the yaw damper systems. However, the air data computer must be installed since the yaw damper Q-potentiometer is used in the system. Voltage through the Q-potentiometer is provided by the yaw damper system. The yaw damper coupler BITE is calibrated with no airspeed inputs to the central air data computer. Removal of black boxes and system components requires normal safety and maintenance precautions such as removal of power prior to removal of components and capping of all exposed electrical connectors. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：737 AMM 飞机维护手册 AUTO FLIGHT 自动飞行 2(45)
